1. Field of the Invention
The present invention relates to a common mode choke coil used for removing noise having the same phase components transmitted from a power supply line or a signal line, and, more particularly, the present invention relates to a small, surface-mountable chip-type common mode choke coil which is used in various electronic circuits.
2. Description of the Related Art
A chip-type common mode choke coil having a winding is available as a chip-type common mode choke coil. In the winding type, a wire is wound upon a winding core portion, and a first end terminal and a second end terminal of the wire are connected to electrodes provided on flanges, one being provided on each end of the winding core portion.
There is one kind of conventional winding, chip-type common mode choke coil formed in the following way. For example, as shown in FIGS. 8A and 8B, flanges 53 are disposed, one on each end of a winding core portion 52. In addition, using immersion, for example, electrode films 56 are applied to legs 55 having grooves 54 on the flanges 53 in order to form four leg-shaped electrodes 57a, 57b, 57c, and 57d, whereby a core 51 is produced. Using the core 51, as shown in FIG. 9, two wires 58a and 58b are wound upon the winding core portion 52 in order to electrically connect the first and second end terminals thereof to the corresponding electrodes (the electrodes 57c and 57d in FIG. 9) by, for example, thermocompression bonding. Then, as shown in FIG. 10, a top plate 60 is mounted so as to cover the top surface of the resulting structure.
However, in the above-described conventional chip-type common mode choke coil, since the grooves 54 are provided in the flanges 53, each of the legs 55 is thin (that is, has a small cross-sectional area in plan view), so that each of the legs 55 may not have sufficient mechanical strength. This results in the problem that the choke coil is not sufficiently reliable.
In connecting exposed conductors (wire bodies) 59a and 59b of the terminals of the corresponding wires 58a and 58b to the corresponding leg-shaped electrodes 57a to 57d, the problem that the wire 58a comes into contact with the electrode 57d adjacent to the electrode 57c at, for example, location A, and is, thus, shorted arises. Even if the wire 58a does not come into contact with the electrode 57d, the problems of reduced withstand pressure and insufficient insulation occur when it cannot be separated therefrom by a sufficient distance.
There is another kind of conventional winding, chip-type common mode choke coil that is produced in the following manner. For example, as shown in FIG. 11, flanges 53 without grooves are provided, one on each end of a winding core portion 52, and a plurality of electrodes 57a, 57b, 57c, and 57d are disposed on the corresponding flanges 53 at predetermined intervals so as not to be brought into electrical conduction with each other, whereby a core 51a is produced. Using the core 51a, as shown in FIG. 12, the beginning end and the termination end of each of the two wires 58a and 58b wound upon the winding core portion 52 are electrically connected to the predetermined electrodes (the electrodes 57c and 57d in FIG. 12) by, for example, thermocompression bonding. Then, as shown in FIG. 13, a top plate 60 is mounted so as to cover the top surface of the resulting structure.
In this kind of chip-type common mode choke coil, since grooves are not provided in the flanges 53, the mechanical strengths of the legs are high. However, as shown in FIG. 12, when the wires 58a and 58b are joined to the electrodes 57c and 57d, a high-temperature heater chip 61 used for removing the films of the wires 58a and 58b may remove not only the portions thereof that are connected to the electrodes 57c and 57d, but also the film of a nearby portion 62. This may, in particular, cause an exposed conductor 59b (wire body) of the wire 58b to get shorted to respect to the adjacent electrode 57c, so that the choke coil has very low reliability.
The problem that a short circuit failure tends to occur similarly occurs in the previously described choke coil shown in FIGS. 8 to 10.
Although, in the two conventional examples, the two-circuit, chip-type common mode choke coils are described as having the aforementioned problems, chip-type common mode choke coils having three or more circuits also have the aforementioned problems.
In addition, although, in the two conventional examples, chip-type common mode choke coils that are provided with top plates are described as having the aforementioned problems, chip-type common mode choke coils which are not provided with top plates also have the aforementioned problems.
In order to overcome the problems described above, preferred embodiments of the present invention provide a highly reliable chip-type common mode choke coil which prevents a wire from being short-circuited as a result of coming into contact with an adjacent electrode, prevents the withstand pressure from being reduced, and ensures sufficient insulation, while providing sufficiently high mechanical strength because its legs have large cross-sectional areas.
According to a preferred embodiment of the present invention, a chip-type common mode choke coil includes a winding core portion, flanges disposed on both ends of the winding core portion, respectively, a plurality of electrodes disposed on each of the flanges at a predetermined distance from each other so as not to come into electrical conduction with each other, and a plurality of wires wound upon the winding core portion, beginning ends and termination ends of the wires being connected to predetermined electrodes of the plurality of electrodes, wherein protrusions which protrude in an axial direction of the winding core portion are provided in areas between the respective electrodes, at inside surfaces of the respective flanges disposed on both ends of the winding core portion.
By arranging protrusions to protrude in the axial direction of the winding core portion in areas between the corresponding electrodes, at the inside surfaces of the flanges, the stroke distances between the adjacent electrodes are increased, and the adjacent electrodes can be separated from each other by the corresponding protrusions. Therefore, it is possible to reliably prevent the occurrence of a short circuit caused by the wires coming into contact with not only the electrodes to which they are primarily to be connected, but also with the electrodes adjacent thereto.
Therefore, even in the case where not only the portions of the films of the wires which are connected to the electrodes, but also nearby portions thereof are removed when the wires are joined to the corresponding electrodes, for example, by pushing a high-temperature heater chip against the wires, it is possible to prevent the occurrence of a short circuit caused by the wires coming into contact with the corresponding adjacent electrodes, and the occurrence of reduced insulation resistance. Therefore, it is possible to obtain a highly reliable chip-type common mode choke coil.
Since the cross-sectional areas of the flanges (that is, the legs) become larger in correspondence with the protrusions, it is possible to obtain a highly reliable chip-type common mode choke coil having excellent mechanical strength.
In the description of preferred embodiments of the present invention, the phrase xe2x80x9careas between the corresponding electrodes, at the inside surfaces of the flangesxe2x80x9d is to be broadly interpreted to refer to the areas between the corresponding electrodes and the areas in the vicinity thereof when the electrodes are disposed on the inside surfaces of the flanges (that is, the opposing surfaces of the two flanges), and to the areas of the inside surfaces of the flanges connected to (formed in correspondence with) the areas between the electrodes on the bottom surfaces when the electrodes are disposed on only the bottom surfaces of the flanges.
The shape in plan view of the protrusion provided on each flange may be at least one of a substantially triangular shape, a substantially rectangular shape, a substantially square shape, a substantially trapezoidal shape, and a substantially semicircular shape.
In preferred embodiments of the present invention, although the shape of the protrusion disposed on each of the flanges is not particularly limited, when it is at least one of a substantially triangular shape, a substantially square shape, a substantially rectangular shape, a substantially trapezoidal shape, and a substantially semicircular shape in plan view, it is possible for the protrusions to increase the stroke distances between adjacent electrodes, to reliably separate the adjacent electrodes, and to prevent the occurrence of short circuits caused by the wires not only coming into contact with the electrodes to which they are primarily to be connected, but also with the electrodes adjacent thereto. Therefore, preferred embodiments of the present invention provide much more effective components.
In the present invention, the shape of each protrusion in plan view may be a combination of at least two of a substantially polygonal shape, such as a substantially triangular shape or a substantially square shape, a substantially trapezoidal shape, a substantially semicircular shape, and other suitable shapes.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the detailed description of preferred embodiments thereof with reference to the attached drawings.